Multi piece turpocharger housing

ABSTRACT

A turbocharger casing including a first casing part, wherein an oil line starts at a first opening on an outer side of the first casing part, runs through the first casing part and opens out at a second opening of a substantially hollow-cylindrical bearing receptacle of the first casing part. Such turbocharger casings of the prior art are produced in a complicated manner by a sand casting process and therefore give rise to high production costs. The teaching is to arrive, without functional losses, at a simple-to-produce and cost-effective turbocharger casing by the turbocharger casing having a second casing part attached to the first casing part and by both casing parts together forming a cooling water line provided for cooling the bearing receptacle. It is thus possible to arrive at a lightweight turbocharger casing by conventional machining production methods and joining technique, and this turbocharger casing can be produced cost-effectively.

The invention concerns a turbocharger housing in which an oil duct starts at a first opening of an outer side of the first housing part, extends right through the first housing part to open at a second opening into a substantially hollow cylindrical bearing receptacle of the first housing part. The invention further concerns a turbocharger comprising such a housing.

BACKGROUND

Turbochargers are used for improving the performance of internal combustion engines in which the kinetic energy of the exhaust gas stream is extracted with help of a turbine and is used to press the fuel-air mixture into the internal combustion engine with help of a common shaft of the turbine and of a compressor. In this way, the fixed cubic capacity of the internal combustion engine can be filled with larger quantity of the mixture so that a higher lifting force and thus also a higher engine performance is achieved during combustion.

In passenger vehicles, turbochargers or rather the shaft of the turbocharger reaches a speed of rotation of more than 200,000 rotations per minute. In the case of utility vehicles, this value is in the order of magnitude of 150,000 rotations per minute. As a rule, the shaft of the turbocharger is mounted in the turbocharger housing through a sliding bearing, with the consequence that a large amount of friction energy is released in the form of heat exactly inside the bearing receptacle of the turbocharger housing. Moreover, the turbocharger housing is situated between the so-called hot housing and the cold housing. In the hot housing, the exhaust gas stream is routed to the turbine so that additional heat is transmitted through the hot exhaust gas stream to the hot housing. During operation, a temperature of typically 1050° C. prevails in the hot housing and in the cold housing, in contrast, where the fuel-air mixture is compressed, the prevailing temperature is approximately 20° C.

For these reasons, it is necessary to cool the turbocharger housing with help of a water cooling, sustainably and in particular in the vicinity of the bearing receptacle. On the one hand, it must be prevented that heat finds its way out of the exhaust gas stream via the turbocharger housing into the cold housing, which can typically also take place via the shaft. On the other hand, it is also necessary to discharge the friction heat that is produced in the sliding bearing. An eventual failure of the cooling of the turbocharger housing creates a risk of damage to the sliding bearing and a premature ignition of the fuel-air mixture in the cold housing.

WO 2009/013332 A3 discloses a turbocharger comprising a housing, said housing being destined to receive a sliding bearing for the shaft of the turbocharger. This housing substantially comprises a cast part that contains a water conduit for cooling the bearing receptacle. The larger part of the water cooling is completely surrounded by the housing both in radial and in axial direction.

Turbocharger housings made out of cast metal do indeed manifest an excellent thermal conductivity but possess, on the other hand, a heavy weight and give rise to very high manufacturing costs precisely due to the very complex integration of the cooling water conduit which, however, is indispensable.

SUMMARY OF THE INVENTION

It is an object of the present invention is to provide a turbocharger housing of a lighter weight that is simple and economic to manufacture without prejudicing the mode of functioning of the turbocharger housing.

The present invention procides a turbocharger housing of the pre-cited type by the fact that the turbocharger housing comprises a second housing part connected to the first housing part, and said two housing parts together form a cooling water conduit for cooling the bearing receptacle.

According to the invention, an oil supply arrangement in form of an oil duct is disposed in the turbocharger housing and serves to supply oil to the bearing arranged in the hollow cylindrical bearing receptacle. For this purpose, the first housing part comprises a first opening that is arranged on an outer side of the first housing part. The oil duct begins at this first opening and extends right through the first housing part. This oil duct can be realized or configured in the first housing part, for example, through appropriate bores. The oil duct ends at a second opening of the first housing part and opens into the substantially hollow cylindrical bearing receptacle. The bearing receptacle, too, is configured on the first housing part by a machining method, for example by boring. If necessary, diverse grooves or annular configurations are provided on the hollow cylindrical inner surface of the bearing receptacle so that, if need be, the bearing receptacle deviates from the substantially hollow cylindrical shape. The second opening thus constitutes the opening of the oil duct into the bearing receptacle so that the sliding or rolling bearing of the turbocharger can be supplied with oil.

In the case of sliding bearing mounted turbochargers, for instance, the lubricant oil is pressed from outside under appropriate pressure into the bearing receptacle so that a so-called squeezable film is formed between the bearing receptacle and the sliding rings and migrates further little by little in axial direction till it finally leaves the sliding bearing.

In addition to the first housing part, the turbocharger housing according to the invention also comprises a second housing part that is connected to the first housing part. The connection can be realized through a known joining method, for example by welding, gluing, crimping and/or soldering. Laser welding is particularly suitable because this guarantees an industrial manufacturing with a very short manufacturing time. The connection of the second housing part to the first housing part results in the formation of a cooling water conduit that is provided for cooling the bearing receptacle. In other words, a part of the outer surface of the first housing part and a further part of the outer surface of the second housing part together form the inner wall of the cooling water conduit. This has the advantage that the cooling water conduit does not have to be manufactured by a complex and expensive casting method but both the housing parts made according to the invention can be manufactured by usual machining methods or by shaping technics and can be connected to each other after this finishing step.

Advantageously, the first housing part is made out of a forged part by a machining method, for instance boring, turning and/or milling. Alternatively, the first housing part may also be made out of sheet metal in which case, care must be taken to assure a heat flow and a cooling effect. The second housing part can likewise be manufactured by a particularly low-cost method by configuring it as a sheet metal part, in particular as a cold-formed sheet metal part. By reason of the possibility of using machining methods, it also becomes possible, in contrast to the cooling chamber in the interior of conventional cast parts, to clearly enlarge the cross-section of the cooling water conduit with very close manufacturing tolerances so that it is advantageously possible through the invention to achieve a cooling water through-put of up to four times the through-put hitherto possible, while keeping the outer dimensions unchanged.

In one advantageous form of embodiment of the invention, the connection of the second housing part to the first housing part is constituted by two connecting seams extending along the cooling water conduit. A connecting seam results from one of the joining methods used. In the case of welding, for instance, this would be a weld seam and, in the case of gluing, a glued seam, etc. An advantage of these methods over casting in sand is that the hollow spaces of the cooling water conduit do not have to be subsequently freed from residual sand under high water pressure. In addition, bores for removing the sand core are not required in the first place.

The connecting seam must not only guarantee the structural stability of the turbocharger housing but also assure a tightness of the cooling water conduit that excludes a leakage of cooling water under the conditions prevailing during operation. In this sense, the connecting seams also have a sealing function.

If the second housing part is made partially or completely out of sheet metal, it is not necessary to conduct a heat flow through the connecting seam because the sheet metal, due to its small thickness, can absorb only a relatively small amount of heat. Cooling therefore takes place via the water conduit mainly through the first housing part. Alternatively, the first and the second housing part are made as cast parts so that both housing parts can accommodate and conduct larger heat streams, and this can become necessary depending on the turbocharger application. Alternatively, for example, if temperature load is low, the first and the second housing part may also be made out of sheet metal.

Advantageously, the first housing part is intended for connecting to a cold housing and/or a hot housing. From the point of view of assembly, it is appropriate to screw the cold housing, the hot housing and the turbocharger housing to one another. The connections between these housings may, however, be realized through other known fixing means. It is, however, important that a housing part of the turbocharger housing eventually made out of sheet metal does not participate in the transmission of the torque of the screw connection. Therefore, for example, spacing bushings for screwing the first housing part to the hot housing or the cold housing are advantageously used in this type of fixation for by-passing a sheet metal housing part. The spacing bushings thus substantially outline the axial width of the second housing part that has to be spanned by this fixation. The advantage of this is that the second housing part, due to a smaller overall contact surface, must not participate at all, or only to a small extent, in a heat transmission from the hot housing to the turbocharger housing part but, rather, a further advantageous insulation is produced due to the distance and due to the spacing bushings. Moreover, spacing bushings are particularly suitable for taking up joining and vibration forces that can be produced during assembly and operation.

Depending on the case of use, it is possible instead of using spacing bushings to make the second housing part more stable (e.g. double walls or the like) so that the second housing part can be braced between the first housing part and the hot housing.

In a further advantageous form of embodiment, a third housing is provided for forming a fixing adapter for fixing the first housing part to the cold housing. Basically, it is possible to configure the first housing part such that a direct fixing on the cold housing is possible. Because, however, this third housing can optionally also be formed out of sheet metal, a further cost advantage is created due to the multi piece structure. Fixing of the third housing part on the first housing part may also be realized through screwing or laser welding or any other type of mechanical connection.

In a further advantageous form of embodiment, a fixing means like, for instance, a screw is used both for screwing the first housing part to the hot housing and for fixing the third housing part to the first housing part. This simplifies the fixing of the turbocharger housing in a two piece or multi piece configuration because the same fixing means can be used in both cases.

The turbocharger housing of the invention can be used both in rolling bearing mounted and in sliding bearing mounted turbochargers. The turbocharger housing can still be made out of more than two or three parts, each part being specially intended for one or more functions. What is important is that one of the housing parts constituting the cooling water conduit has an adequate mass for assuring an optimal conduction of heat to the cooling water conduit.

Further advantages and preferred developments of the invention can be seen in the description of the figures and/or the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described and explained more closely in the following with reference to the forms of embodiment illustrated in the appended drawings. The figures show:

FIG. 1, a sliding bearing mounted turbocharger comprising a three piece turbocharger housing, in a longitudinal section along the axis of rotation,

FIG. 2, the first housing part of the turbocharger housing of FIG. 1 made as a machine-finished forged part, in a longitudinal section along the axis of rotation,

FIG. 3, the first housing part of the turbocharger housing of FIG. 1, as viewed along the vertical axis,

FIG. 4, the first housing part of the turbocharger housing of FIG. 1, as viewed along the axis of rotation,

FIG. 5, the second housing part of the turbocharger housing of FIG. 1, as viewed along the axis of rotation,

FIG. 6, the second housing part of the turbocharger housing of FIG. 1, in a first sectional illustration vertical to the axis of rotation,

FIG. 7, the second housing part of the turbocharger housing of FIG. 1, in a second sectional illustration vertical to the axis of rotation,

FIG. 8, the third housing part of the turbocharger housing of FIG. 1, as viewed along the axis of rotation, and

FIG. 9, the third housing part of the turbocharger housing of FIG. 1, in a sectional illustration vertical to the axis of rotation.

DETAILED DESCRIPTION

FIG. 1 shows a sliding bearing mounted turbocharger comprising a three piece turbocharger housing, in a longitudinal section along the axis of rotation R. The first housing part 15 of the turbocharger housing is configured as a machine-finished forged part, in longitudinal section along the axis of rotation R.

The turbocharger housing comprises the first housing part 15, the second housing part 7 and the third housing part 16. The turbocharger housing is arranged between the cold housing 1 and the hot housing and screwed to both of these housings.

The shaft 19 connects the turbine 10, which is arranged in the hot housing 12, to the compressor 17 which is fixed on the shaft 19 with help of a fixing element 18, e.g. a nut. The shaft 19 is configured in one piece with turbine 10 so that, due to heat conduction, a basic danger of heat migrating out of the hot housing 12 into the cold housing 1 exists.

The water conduit 11 comprises a sectional surface of a square or at least rectangular shape, possesses a substantially annular shape and surrounds a part of the sliding bearing in radial direction. The water conduit 11 is also often called cooling chamber or water pocket. The water conduit 11 is formed and defined partially by the first housing part 15 and partially by the second housing part 7. The connecting seams 9, 14 are made through a joining method such as, for example, laser welding and lead to a structural stability of the turbocharger housing while additionally sealing the water conduit 11 so that cooling water can exit.

The connecting element 13 is substantially configured in the form of a tube and welded to the second housing part 7. The connecting element 13 provides an advantageous connecting junction for a cooling water hose. The connecting element 13 can function optionally as an inlet or an outlet.

The third housing part 16 is configured as a sheet metal part which leads to a cost advantage because a relatively favorable cold shaping replaces a machining fabrication method. Alternatively, the third housing part 16 can be configured in one piece with the first housing part 15 in so far as a multi piece configuration is not desired or if, for example, the turbocharger housing is desired to have a two piece structure.

The third housing part 16 is pressed in radially into the cold housing 1 and additionally screwed to this.

The sliding bearing of the turbocharger comprises sliding bearing rings 8 that are supplied with oil through oil ducts 3, 5. The spacers used are in the form of spacing rings 6.

FIGS. 2 to 4 show the first housing part 15 in different views. The first housing part 15 is a forged part comprising a lubricant duct system which is subsequently configured in the form of bores in the forged part. The oil duct 3 comprises a first opening 2 on an outer surface of the housing part 15, extends radially towards the axis of rotation R and branches into an inclined oil duct 5 that extends substantially in axial direction but also slightly inclined relative to the axis of rotation to open into the bearing receptacle 20 at an opening, not referenced.

The outer radii of the housing part 15 are made by turning which means that they are likewise made by a machine finishing. An advantage of this is that the thus obtained cylindrical and disk-like surface can be finished with a very high precision and, together with the second housing part, not shown, can form a water conduit that can thus also be realized with a very high precision.

In FIG. 4, the direction of viewing extends along the axis of rotation to the side of the first housing part 15 facing the cold housing 1. To be seen are bores 24 that extend with variable bore spacing relative to one another (as projected on the horizontal axis Z and the vertical axis Y respectively). The bores 24 serve on the one hand to attach the third housing part and, on the other hand, to connect the first housing part to the cold housing and the hot housing. The variable bore spacing chosen assures that the components are screwed together with the correct relative orientation. A combination of the bore spacings A, B, C assures that the components are always in the correct position relative to one another.

FIGS. 5 to 7 show the second housing part 7 in different views. The second housing part 7 substantially possesses the shape of a bushing whose bushing bottom comprises a depression that projects axially out of the bushing and in which a bore 23 has been made.

Further, the second housing part 7 comprises in the cylindrical part an opening 22 and/or an opening comprising a connecting element 21. Through such openings, it is assured that the cooling water can flow into the water conduit 11 that is formed partially by the second housing part 7.

The edges of the bore 23 as also the edges of the opposing (largest) circular opening of the second housing part 7 participate in so far in the welding joint with the first housing part 15 that a part of the material, in addition to the material specially brought in by the joining step, likewise contributes to forming the weld seam. It can be seen that the connecting seams are two closed, i.e. annular joints.

FIGS. 8 and 9 show the third housing part 16 of the turbocharger housing comprising four bores 25 that are arranged identically to the bores 24 of the second housing part. During the screwing of the first housing part 15 to the hot housing 12, it is thus possible to fix the third housing part 16 on the first housing part in the same work step. For this purpose, four screws must first be inserted through bores, not shown, of the cold housing 1, after this, through the bores 25, following this, through the bores 24 and then through spacing bushings, not shown, to be finally screwed into the hot housing 12. In this way, four screws are sufficient for assembling the entire turbocharger.

The third housing part 16 comprises, radially inside, a cylindrical axial extension 26 that serves for the axial spacing of the cold housing 1. The outer periphery of the third housing part 16 that is configured as a fixing adapter is chosen such that the third housing part 16 can be pressed into the cold housing 1. This simplifies assembly during which the third housing part 16 fulfills a retaining function as long as the screwed connection has not been made.

LIST OF REFERENCE NUMERALS

1 Cold housing

2 First opening

3 Oil duct

4 Second opening

5 Inclined oil duct

6 Spacing ring

7 Second housing part

8 Sliding bearing

9 Connecting seam

10 Turbine

11 Cooling water conduit

12 Hot housing

13 Connecting element

14 Connecting seam

15 First housing part

16 Third housing part

17 Compressor

18 Fixing element

19 Shaft

20 Bearing receptacle

21 Connecting element

22 Opening

23 Bore

24 Bore

25 Bore

26 Axial extension

A Bore spacing

B Bore spacing

C Bore spacing

R Axis of rotation

Y Vertical axis

Z Horizontal axis 

1-10. (canceled)
 11. A turbocharger housing comprising: a first housing part, an oil duct starting at a first opening of an outer side of the first housing part, extending right through the first housing part to open at a second opening into a substantially hollow cylindrical bearing receptacle of the first housing part, and a second housing part connected to the first housing part, the first and second housing parts together forming a cooling water conduit for cooling the bearing receptacle.
 12. The turbocharger housing as recited in claim 11 wherein the second housing part is connected to the first housing part by at least one of gluing, welding, crimping and soldering.
 13. The turbocharger housing as recited in claim 12 wherein connection of the second housing part to the first housing part is formed by two connecting seams extending along the cooling water conduit.
 14. The turbocharger housing as recited in claim 11 wherein the cooling water conduit and the oil duct of the first housing part are machine finished.
 15. The turbocharger housing as recited in claim 11 wherein the first housing part connectable to at least one of a cold housing and a hot housing.
 16. The turbocharger housing as recited in claim 15 wherein the first housing part is screwable to the hot housing using spacing bushings.
 17. The turbocharger housing as recited in claim 15 further comprising a third housing part forming a fixing adapter for fixing the first housing part to the hot housing.
 18. The turbocharger housing as recited in claim 17 further comprising a fixing element both for screwing the first housing part to the hot housing and for fixing the third housing part to the first housing part.
 19. The turbocharger housing as recited in claim 11 wherein the second housing part or a third housing part is made out sheet metal or out of a forged part.
 20. A turbocharger comprising: a bearing for a common shaft of a compressor; a turbine; and the turbocharger housing as recited in claim 11, the bearing being arranged in the bearing receptacle. 